An attack by suspected ISIS militants on a border guard base near the Syrian border left at least 16 killed and four others seriously wounded according to Faleh al-Issawi , the deputy head of the Anbar provincial council in Iraq .

The militants slaughtered the 16 border guards , including their commanding officer , in a surprise early morning attack on Monday , al-Issawi said .

Four others are in critical condition , he said .

The base attacked is near al-Waleed border crossing , the only crossing Iraq has with Syria that is still controlled by Iraqi forces . ISIS maintains control of almost all of Anbar -- Iraq 's largest province .

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Suspected ISIS militants killed 16 Iraqi border guards , official says

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Official : Four others in critical condition

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Base is only one with Syria that is still controlled by Iraqi forces